Helical Pitches and Tilt Angles in Room Temperature Ferroelectric Chiral Smectic C Liquid Crystals, MORA n and MBRA n

Abstract

The helical pitches and the tilt angles are measured as a function of temperature for recently synthesized room temperature ferroelectric Sm C* liquid crystals to examine the possibility as materials for switching devices. The pitch of MBRA 8 is almost independent of temperature except in the range close to the Sm A to Sm C* phase transition, where it appears to decrease steeply as in nOBAMBC. In MORA 8 and 12, it gradually increases with temperature but does not decrease near the transition from Sm C* to isotropic. The tilt angle of MBRA 8 is relatively small as compared with the desired value of 22.5° for the best contrast. The tilt angle of MORA n could not be determined because the spontaneous polarization is too small to unwind the helix for the measurements. The present substances are not suitable for switching devices by themselves, but are pointed out to be useful as mixing components.

Identification of the Liquid Crystal Phases of some Chiral Schiff Bases

“…The pitch values obtained here are somewhat lower than those measured on diffraction patterns. 21 The pitch of the twisted smectic C phase of 2-8 has been previously measured. 27…”